Reciprocating magnetic means for operating snap action mercury switch



March 31, 1970 v M'. BEKEDAM 3,

- RECIPROCATING MAGNETIC MEANS FOR OPERATING SNAP ACTION MERCURY SWITCH Filed Nov. 13, 1967 v 2 Sheets-Sheet 1 III 111 I1 IIIIIIIIIIIIIIIIA I I I 11 1 I I mvsmon MARTIN BEKEDAM- BYW' L ATTORNEY March 31,1970 1 M. BEK'EDAM I 3,50 1

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' med Nov. is; V1967 mvm N 3 1.1 g .'5 MARTIN seat-mm ATTOR EV United States Patent F RECIPROCATING MAGNETIC MEANS FOR OPERATING SNAP ACTION MERCURY SWITCH Martin Bekedam, Orinda, Calif. (1231 16th Ave., Oakland, Calif. 94606) Filed Nov. 13,1967, Ser. No. 682,222 Int. Cl. Hlf 7/02 US. Cl. 335306 Claims ABSTRACT OF THE DISCLOSURE My device uses two spaced apart disc-shaped holding magnets mounted on a stem that can be moved'in the direction of its length. One face of each magnet is of one polarity and the other face is of opposite polarity. A semi-circular magnet is pivotally mounted between these two disc magnets and the magnetic field of this magnet always lies between the magnetic fields of the two holding magnets. Magnetizable stop pins limit the swinging movement of the semi-circular magnet and cause a snap action operation by this magnet.

A modified form of the device includes a central disc magnet mounted on the stem and between the two holding magnets. The semi-circular pivoted magnet will have its magnetic field placed between the magnetic fields of one holding disc magnet and the central disc magnet When in one position; and will have its magnetic field lie between the fields of the other holding disc magnet and the central disc magnet when it is in its other position. The pivoted magnet will have a snap action between these two positions.

BACKGROUND OF THE INVENTION (1) Field of the invention It has been the practice in steam boilers and the like to provide automatic means for maintaining the water level in the boiler at a selected level. This is usually accomplished by providing a float control switch which will be closed when the water level falls below the pre determined level. The closing of the switch starts a motor driven pump that will add water to the boiler until the selected level is reached. The float or fluid displacer is mounted on a stem and the latter actuates the switch. The motor actuating switch should be of the snap action type, but the water level in a boiler changes so slowly that the slow movement of the stem caused by the float or dis placer will not produce a snap action.

(2) Description of the prior art In my Patent No. 3,167,694, issued Jan. 26, 1965, on a Permanent Sensing Element of Limited Rotation Operating Snap Action Electric Switches, I disclose :a floatactuated stem that moves a disc-sensing magnet past a semi-circular magnet which in turn is mounted in a rockably supported frame. The poles of the two magnets are arranged to cause a snap action to the frame as the sensing magnet is moved past the semi-circular magnet. A stationary holding magnet is positioned with respect to the semi-circular magnet for holding it and the frame in either one of two positions into which it has been snapped by the movement of the sensing magnet caused by the float moving the stem.

carries a semi-circular magnet. The magnet has one polarity on one face and an opposite polarity on the other 3,504,316 Patented Mar. 31, 1970 face. This magnet has its magnetic field always lying within the magnetic fields of two spaced apart disc magnets that are mounted on a stem which is movable in the direction of its length. Each disc magnet has one polarity on one face and an opposite polarity on the other face. In one form of my invention, the limit stops for determining the amount of swing of the rockable member are formed of magnetizable material and are positioned so that one of the stops. will contact with the semi-circular magnet when the rockable member swings into one extreme position and the other stop will contact with the semi-circular magnet when the member swings into its other extreme position. The novel snap action of the rockable member is produced by the magnetic attraction between the semi-circular magnet and the magnetized stop that it contacts during the initial movement of the stem and its two disc magnets in an axial direction that will tend to swing the semi-circular magnet from its contacted stop to the other stop. The magnetized contacted stop will delay any swinging of the semi-circular magnet until this magnetism is broken whereupon the semi-circular magnet will have a snap action as it moves from the contacted stop to the other stop.

In the modified form of the invention, the stops are made of non-magnetizable material and a center disc magnet is added to the stem and is disposed between the two holding disc magnets The rockable member with its semi-circular magnet is positioned so that the magnetic field of this magnet will either lie between the magnetic fields of the center disc magnet and one of the holding disc magnets or will lie between the magnetic fields of the center disc magnet and the other holding disc magnet. The snap action of the rockable member is caused by the stem moving the center magnetic disc past the semi-cir cular magnet. The rocking of the member can be used for actuating mercury or micro switches or for any other function desired. In both forms of the invention the pivoted U-shaped magnet is bound in a magnetic field and does not require a spring to pull it in or out of the field. Therefore the U-shaped magnet is in a constantly engaged magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a vertical section through the device, portions being shown in elevation, and illustrating one form of my invention.

FIGURE 2 is a horizontal section taken along the line 2-2 of FIGURE 1.

FIGURES 3 to 5 inclusive are three schematic diagrams omitting the non-magnetic tube and illustrating the semi-circular magnet as being positioned to .the right of the vertically movable stem rather than encircling the stem as shown in FIGURES 1 and 2. This is for the purpose of more clearly illustrating the purpose and func' tion of the various magnetic fields surrounding the magnets.

FIGURES 6 and 7 are schematic diagrams of a modified form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In carrying out my invention, I show in FIGURE 1, one use of my invention by way of example. A tank indicated generally at A, carries water or other fluid. A chamber B is associated with the tank for indicating the level of the fluid therein. An upper interconnecting pipe 1 extends between the tank and the chamber and a lower interconnecting pipe 2 extends from the bottom of the chamber to the bottom of the tank. The top of the chamber B may be secured to an assembly base C.

My device is mounted in a housing indicated generally 3 at D in FIGURE 1. The housing has a bottom wall 3 that has a central opening for receiving the upper portion of a coupling member E. The coupling member has a lower threaded end E1 that is received in a threaded opening 4 provided in the base C. The upper portion E2 of the coupling E is threaded and receives a washer 5 that rests on the nut-shaped central portion 6 of the coupling member. The bottom wall 3 of the housing D rests on the washer and a nut 7 is threaded onto the upper portion E2 for clamping the bottom wall in place.

A non-magnetic tube F is sealed in the bore of the coupling member E, see FIGURE 1. This tube has a closed upper end 8 and a threaded stud projects upwardly from this end. A dome-shaped cover 9 has a central opening for receiving the stud and a nut 10 is screwed onto the stud for removably securing the cover in place. The lower end of the dome-shaped cover 9 overhangs an upwardly turned annular flange provided on the bottom wall 3.

Within the non-magnetic tube F, I slidably mount a stem G and a holding disc-shaped magnet H is mounted at the top of the stem and it slides in the bore of the tube, see FIGURE 1. The entire upper face of the disc magnet is a North pole, which is indicated by the letter N, and the entire lower face is a South pole and is indicated by the letter S. A non-magnetic spacing sleeve 11 is next mounted on the stem and its upper end contacts with the underside of the disc magnet H. A lower holding disc-shaped magnet J is mounted on the stem G and bears against the bottom of the sleeve 11. Another spacing sleeve 12 is mounted on the stem and abuts the underside of the disc magnet J. A spring-pressed disc 13 is slidably mounted on the stem and is yieldingly held against the lower end of the sleeve 12 by a coil spring 14. A base disc 15 is slidably mounted on the stem and is held in place by a split locking ring 16 that in turn is removably held in an annular groove provided in the bore of the coupling member E. The coil spring 14 yieldingly holds the magnets H and J and the sleeves 11 and 12 as well as the disc 13 in assembled relation. The lengths of the sleeves may be varied to permit the disc magnets to be placed the desired distance apart. The stem G slides in a central opening provided in the base disc 15.

The lower end of the stem G is connectced to one or more liquid displacers K, shown in FIGURE 1. The displacer may be adjustably mounted on the stern. I have shown the liquid displacer received in the chamber B where the liquid level 17 will be the same as the liquid level in the tank A. It is possible to have the base C mounted directly on the tank and have the stem G and the liquid displacer K project into the liquid in the tank. In this way the chamber D could be dispensed with. The stem G can be moved in the direction of its length by other means than that shown in FIGURE 1. When the displacer K is used instead of a float, the coil spring 14 will oifset the weight of the displacer as well as the weight of the stem G.

I provide a rocka'ble carriage L for supporting a mercury switch M, and a semi-circular magnet P, see FIG URES 1 and 2. A platform Q is adjustably supported by a threaded post 18 and held in place by nuts 19. The platform is of non-magnetic material and it has an opening 20, through which the non-magnetic tube F extends. The platform Q and the carriage L are placed within the housing D. A U-shaped pivot support 21 is mounted on the platform Q and the carriage L is pivotally mounted on the support 21 at 22. The carriage L is also U-shaped and its arms support the ends of the semi-circular magnet P, at 23, see FIGURE 2. The semi-circular magnet P encircles substantially one half of the cylindrical tube F, and it is disposed close to the outer surface of the tube. FIGURE 1 shows the magnet P positioned between the two holding disc magnets H and J. An iron stop screw R is adjustably mounted on the non-magnetic platform Q fit and the magnet P comes to rest on this screw when it is in one of its two positions. As soon as the magnet P contacts the iron screw R, the screw becomes magnetized and there will be a magnetic attraction between the two which I utilize for delaying the upward swinging of the magnet P during the initial upward movement of the stem G. This will be explained shortly.

A non-magnetic bracket 24 is mounted on the platform Q, see FIGURES 1 and 2, and it carries an adjustable upper iron screw T. The semi-circular magnet P on its upward swinging movement with the carriage L contacts the upper stop screw T, and magnetizes it. This will create a magnetic attraction between the magnet P and the stop T and I utilize this for delaying the downward swinging of the magnet during the initial downward movement of the stem G. This will be explained in the operation of the device. The carriage L may be balanced in its swinging movement on the pivot 22 by a counterbalance weight 25 that is placed opposite to the magnet P. A wire terminal block U has wires, not shown, leading from it to the mercury switch M. One or more openings, not shown, may be provided in the bottom wall 3 through which other wires, not shown, lead from the terminal block U, and may be used for any purpose desired.

From the foregoing description of the various parts of the device the operation thereof will be readily understood. FIGURES 3, 4 and 5 illustrated diagrammatically the operation. The non-magnetic tube F, has been omitted and the semi-circular magnet P, has been moved to the right side of the stem G so that the fields of flux around the various magnets can be more clearly shown. The iron stop screws R and T, have also been moved to the right and will be contacted alternately by the magnet P, as the latter is swung from one position to the other.

Assume in FIGURE 3 that the semi-circular pivoted magnet P, is in contact with the lower iron stop R, and that the stem G, is being raised vertically by the rising liquid 17 in the chamber B, or by any other means. The upper surfaces of the magnets H, J and P, have a North polarity while the lower surfaces of the same magnets have a South polarity. The magnet P, will magnetize the iron stop R because it is in contact therewith. The holding magnet J has a flux field surrounding it as indicated by the looped lines J. Also the magnet P, has a flux field P surrounding it.

As the stem G raises the magnet J, the two flux fields J and P will be crowded together and will tend to swing the magnet P, clockwise. For a short time the magnetic attraction between the magnet P, and the iron stop R, will delay the swinging of the magnet P. This delay of swinging the magnet permits a certain lost motion to take place with the stem G where the stem will continue to rise without causing the magnet J to impart a clockwise movement to the magnet P. Eventually the crowding of the two flux fields in the ever narrowing space separating the magnets J, and P, will produce suflicient force on the magnet P, to overcome the magnetic attraction between it and the iron stop R. The magnet P will now have a snap action and will quickly swing clockwise into the position shown in FIGURE 4, where the magnet will now contact the upper iron stop T. The repelling force between the swinging magnet P and the lower disc magnet I will limit the upward movement of the stem. The clockwise swinging of the magnet P into the position shown in FIGURE 4 will free the downward pressure on the stern G caused by crowding of the two flux fields J and P prior to swinging and this will permit the stem to move upward more quickly and aid in the snap action swinging of the magnet. As soon as the magnet P contacts the upper iron screw stop T, there will be magnetic attraction between the two. On the reverse downward movement of the stem G, it will have to travel from the position shown in FIG- URE 4 into the position shown in FIGURE 5 before the flux field H for the upper disc magnet H will start to crowd in upon the flux field P' of the swinging magnet P.

Again there will be a lost motion in the downward movement of the stem G before the crowded flux fields H and P' will exert sufiicient force to overcome the magnetic attraction between the magnet P and the iron screw stop T with which it is in contact. The distance between the two disc magnets J and H determines the amount of lost motion of the stem before the swinging magnet is snapped into its new position. This distance can be varied. The swinging of the magnet P and its carriage L can be used for any purpose desired such as actuating mercury or micro switches or air switches.

The heads of the iron stops R and T can be made larger and this will cause more delay before the swinging magnet P will be freed from the stop it is contacting. Also the stop screws R and T could be shifted laterally with respect to the swinging magnet P, and this will vary the amount of magnetic attraction between the magnet and its contacted stop and thus vary the time period when the magnet is freed from its magnetized stop. Any means, not shown, may be used for this lateral shifting of the stops. It will be noted that the pivoted magnet P is bound in a magnetic field in both of its extreme positions and does not require a spring to pull it in or out of the field. The swinging magnet will therefore be in a constantly engaged magnetic field.

MODIFIED FORM OF DEVICE In FIGURES 6 and 7, I show a modified form of the invention. I mount two disc-shaped holding magnets on the vertically movable stem V, an upper magnet W, and a lower magnet X. I further mount a central disc magnet Y on the stem and dispose it midway between the two holding discs. A pivoted semi-circular magnet Z, is shown spaced to the right of the stem V, but in actual practice it would be mounted on a pivoted carriage and would enclose the stem in the same manner as the semicircular magnet P, encircles the stem G, and is mounted on the carriage L, in FIGURES 1 and 2. The semicircular magnet Z is spaced to the right of the stem V, in FIGURES 6 and 7, in order to illustrate the fields of flux that surround the various magnets. The non-magnetic tube F, would enclose the three disc magnets W, X and Y and the semi-circular magnet Z would enclose the tube. A lower non-magnetic stop 50 limits the swinging movement of the magnet Z, in one direction while an upper nonmagnetic stop 51 limits the swinging movement of the magnet in the opposite direction. Both stops are made of non-magnetizable material. The magnet Y is called a sensing magnet.

The top and bottom holding magnetic discs have their South poles S on their upper faces and have their North poles N on their lower faces. The center magnetic disc has its North pole N on its upper face and its South pole S on its lower face while the semi-circular swinging magnet Z also has its North pole N on its upper face and its South pole S on its lower face. All four magnets W, X, Y and Z have their fields of flux W, X, Y and Z, surrounding them as indicated by the oval lines in FIGURES 6 and 7.

Assume that the various parts are in the position shown in FIGURE 6 and that the stern V, is being moved upwardly by any means such as by the displacer K, in FIGURE 1, because the liquid level 17 is rising. The pivoted magnet Z is shown in contact with the upper non-magnetic stop 51. The upper holding magnet W, has a portion of its flux field W merged with a portion of the flux field Z of the pivoted magnet Z. At the same time, there is a repelling force built up between a portion of the flux field Y of the center disc magnet Y, and a portion of the flux field Z of the pivoted magnet Z. Therefore the attracting magnetic force between the top holding magnet W, and the pivoted magnet Z, and the repelling force between the center disc magnet Y and the pivoted magnet will keep the pivoted magnet in con- 6 tact with the upper stop 51, URE 6.

As the stem V moves the center magnet Y, upwardly past the pivoted magnet Z, the flux field Y will have a portion forced through a portion of the flux field Z of the pivoted magnet. Inactual practice since the semicircular magnet Z, encircles the stem V, substantially all of the flux field Z of the magnet Z creates a repelling force of at least one-half of the flux field Y of the center magnet Y. The center magnet Y will be forced through the flux field Z of the pivoted magnet Z, as the stern V moves the center magnet Y upwardly. There will be a snap action of the pivoted magnet Z, in a counter as clearly shown in FIG- clockwise direction as it quickly moves into the position shown in FIGURE. 7, where it will contact with the non magnetic stop 50.

The pivoted magnet Z will be held in its new position in FIGURE 7 by the repelling action of the two flux fields Y and Z and by the magnetic attraction between the lower holding magnet X and the pivoted magnet Z. The reverse snap action takes place when the stem V starts moving downwardly. It is possible for the stem to override a slight distance in its up or down movement and the holding magnets W and X will maintain the swinging magnet Z in the position into which it had just been swung.

The modified form of the invention uses two holding magnets W and X that are mounted on the stem V and move with it. The center magnet Y is used to force through the flux field Z of the pivoted magnet Z to produce the snap action for the magnet Z. In this form of the device the pivoted magnet Z will be bound in a magnetic field in both of its extreme positions and does not require a spring to pull it in or out of the field. It can therefore be said that the pivoted magnet Z will be constantly engaged in a magnetic field.

I claim:

1. In a control mechanism:

(a) a stem movable in the direction of its axis between predetermined limits;

(b) a pair of holding disc magnets mounted in spaced relation on said stem and being movable therewith; each disc magnet having a North pole on one face and a South pole on its opposite face with the same polarities of both discs facing in the same direction;

(c) a pivoted magnet having a curved portion encircling said stem with the center of the curved portion lying substantially on the axis of said stem; one face of said pivoted magnet being of one polarity and the other face being of the opposite polarity; and

(d) a pair of stops for limiting the swinging movement of said pivoted magnet;

(c) said pivoted magnet being positioned between said holding magnets at all times so that its fiux field will be disposed adjacent to one of said holding magnets when said stem has substantially moved into one of its extreme positions and the flux field of said pivoted magnet will be disposed adjacent to the other holding magnet when said stem has substantially moved into its other extreme position;

(f) whereby said pivoted magnet will be constantly engaged by a magnetic field of either one of said holding magnets.

2. In a control mechanism:

(a) a stem movable in the direction of its axis between predetermined limits;

(b) a pair of holding disc magnets mounted in spaced relation on said stem and being movable therewith; each disc magnet having a North pole on one face and a South pole on its opposite face with the same polarities of both discs facing in the same direction;

(c) a pivoted magnet having a curved portion encircling said stem with the center of the curved portion lying substantially on the axis of said stem; onc face of said pivoted magnet being a North pole and facing in the same direction as the North pole faces of said holding magnets, and the other face of said pivoted magnet being a South pole and facing in the same direction as the South poles of said holding magnets; and

(d) a pair of magnetizable stops for limiting the swinging movement of said pivoted magnet;

(c) said pivoted magnet being positioned between said holding magnets so that its flux field will be disposed adjacent to the flux field of one of said holding magnets when said pivoted magnet contacts with the stop disposed closest to the same holding magnet and said stem has substantially moved into one of its extreme positions; and the pivoted magnet flux field will be disposed adjacent to the flux field of the other holding magnet when said pivoted magnet contacts with the other stop and said stem has substantially moved into its other extreme position;

(f)- whereby said pivoted magnet will be constantly engaged by a magnetic field of either one of said holding magnets.

3. The combination as set forth in claim 2, and in which (a) a non-magnetizable tube encloses said holding magnets while permitting the stem to move said magnets within said tube; and

(b) the curved portion of said pivoted magnet is disposed exteriorly of and encircles said tube with the inner surface of the curved portion being disposed close to the tubes outer surface so that the flux field of said pivoted magnet will be acted upon by the flux fields of said holding magnets as the latter are moved by said stem.

4. In a control mechanism:

(a) a stem movable in the direction of its axis between predetermined limits;

(b) a sensing disc magnet mounted on said stern and having a North pole on one face and a South pole on its other face;

() a pair of holding disc magnets mounted on said stem and on either of said sensing disc magnet and in spaced relation therewith, each disc magnet having a North pole on one face and a South pole on its opposite face with the same polarities of both holding magnets facing in the same direction, but with the two North poles facing opposite to the North pole on said sensing disc;

(d) a pivoted magnet having a curved portion encircling said stem with the center of the' curved portion lying substantially on the axis of said stem and the curved portion being large enough to permit said sensing magnet to pass therewith during the movements of said stem; one face of said pivoted magnet being a North pole and facing in the same direction as the North pole of said sensing magnet; the other face of said pivoted magnet being a South pole; and

(e) a pair of non-magnetizable stops for limting the swinging motion of said pivoted magnet;

(f) said pivoted magnet being positioned between said holding magnets so that its flux field will be disposed adjacent to one of said holding magnets when said stem has substantially moved into one of its extreme positions so that there will be a magnetic attraction between the two; and the flux field of said pivoted magnet will be disposed adjacent to the other holding magnet when said stem has moved said sensing magnet past said pivoted magnet while said stem is being moved into its other extreme position and there will be a magnetic attraction between said other holding magnet and said pivoted magnet;

(g) whereby said pivoted magnet will be constantly engaged by a magnetic field of either holding magnet.

5. The combination as set forth in claim 4, and in which:

(a) a non-magnetizable tube encloses said holding magnets and said sensing magnet while permitting the stem to move said magnets within said tube; and

(b) the curved portion of said pivoted magnet is disposed exteriorly of and encircles said tube with the inner surface of the curved portion being disposed close to the tubes outer surface so that the flux field of said pivoted magnet will be acted upon by the flux fields of said sensing and holding magnets as the latter are moved by said stem.

References Cited UNITED STATES PATENTS 4/1957 Thomas.

5 G. HARRIS, Primary Examiner US. Cl. X.R.

1/1965 Bekedam 335-306 XR 

